If you want to do this right take 2 or 3 years, give them a pass rush and a int score then find the correlation coefficient. (excel function between the two lists). You really need to eliminate outliers but that is a little more difficult.

But even if you find a strong coorelation, remember that coorelation does not prove causality. The example I always use is that in the summer people wear shorts more often. People also buy more ice cream cones. If you went back by 2 years you would might get a coorelation of over .90. That does not mean that eating ice cream causes people to want to wear shorts or that wearing shorts makes someone want to eat ice cream.

The point of this is that you can argue that a good pass rush creates interceptions but the opposite might be true. A good secondary can give pass rushers a chance to get to the QB by covering WRs longer. There are other factors in play too. Some teams may have great cover guys who can't catch. They might also have a monster pass rush and guys that can't catch. Good pass rushes might also disuade teams from passing as much. There are so many variables that you really have to look beyond two rankings to find your answer.

edit: was replying to the first post, didn't realize it has been around for 3 years. The first is still a good look but doesn't apply as much because you did more work. The part about coorelation and causality still applies. Also went back and read my rather long def rankings post. I wish I had time to do that stuff today.